S3 MPG Issue

[MarcMiller]

I figured I’d make a new post about this to get more feedback. I’ve had my S3 for 3 weeks. Those 3 weeks I’ve averaged roughly 200 miles to a full tank. I bought the car CPO with 44k and all the service intervals done up to 50k at an Audi dealer.

For the first week or two I thought maybe I was just overly excited and driving with a heavy foot. This last week I’ve switched over to thinking something is really causing me to get this gas mileage. I had a 2016 A3 and that averaged 280-310 miles on a full tank. I figured the S3 wasn’t as good but I still think it should be way more.

I do drive a lot in the city but even fully city driving I should be seeing 250 miles to a full tank. Based on what I’ve been recording I’m averaging roughly 14-15mpg.


Since I’m not the original owner of my car, I’m curious on where to start trying to find the issue. Spark plugs were replaced already, that was my first thought. Where should I start before I start throwing money at things that aren’t causing my bad mpg.

Has anyone on here ran into this issue and found a solution?


Also, while I’m on the topic.... what are some things I should look into as far as preventative maintenance? I swapped my intake and TIP over that I had on my A3 and noticed a good amount of oil in the stock TIP, maybe I should invent in a catch can. I didn’t really run into any issues with my A3 and I was the only owner. I knew my car was running perfect, and had no issues. Plan on owning my car for a long time and would love to learn as much as i can about things to look out for and also things that are common.

[n8vs3]

Intake valve carbon deposits?

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[MarcMiller]

Intake valve carbon deposits?

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Well that’s a new one. Is it common on these cars? My A3 had more miles and i never noticed any issues. How do you go about checking of cleaning it? I’d assume the manifold has to come off?


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[n8vs3]

Intake valve deposits are inherent flaw with direct injection engines... I just raised that as a possibility based on milage of pre-owned S3.

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[40hands]

im all highway for my commute and i probably see 210-220 on a tank. Its definitely much lower than my A3, but the S3 is much more fun to drive.

[Brandon.august]

I have a 2015 S3 with 76k miles. I do a mix of city and highway driving and I hit 300+ miles every tank, roughly 26-27 mpg. Stock. I’m hardly ever in sport/dynamic but I’m always crushing on the highway >80mph.

Did a carbon cleaning, it was a mess in there. Intake manifold has to come off to do this. I also did spark plugs and swapped both MAP sensors.

[MarcMiller]

I have a 2015 S3 with 76k miles. I do a mix of city and highway driving and I hit 300+ miles every tank, roughly 26-27 mpg. Stock. I’m hardly ever in sport/dynamic but I’m always crushing on the highway >80mph.

Did a carbon cleaning, it was a mess in there. Intake manifold has to come off to do this. I also did spark plugs and swapped both MAP sensors.

Thank you! I’m going to look into this. Would you guys suggest I do anything to the fuel system? Maybe fuel filter replacement.


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[Brandon.august]

Thank you! I’m going to look into this. Would you guys suggest I do anything to the fuel system? Maybe fuel filter replacement.


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So the car doesn’t have a traditional fuel filter that’s replaceable as far as I can tell. It has a fuel pump in the fuel tank, located underneath the back seat (there’s a thread on this right now, “A3 stalling issue”). I think you have to replace the entire pump to replace the filter. Then there’s the HPFP on top of the engine, but I’m not sure that’s relevant here.

Have you scanned the car to see if any soft codes have been thrown?

[MarcMiller]

So the car doesn’t have a traditional fuel filter that’s replaceable as far as I can tell. It has a fuel pump in the fuel tank, located underneath the back seat (there’s a thread on this right now, “A3 stalling issue”). I think you have to replace the entire pump to replace the filter. Then there’s the HPFP on top of the engine, but I’m not sure that’s relevant here.

Have you scanned the car to see if any soft codes have been thrown?

First thing I did was scanned it with VAGCOM. No codes. Making this harder lol


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[MarcMiller]

My car is saying I average 16.9mpg right now and the 2nd MPG trip shows 19mpg... either way I feel like they should both be at least 20-24mpg.


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[Brandon.august]

My car is saying I average 16.9mpg right now and the 2nd MPG trip shows 19mpg... either way I feel like they should both be at least 20-24mpg.


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Are you always in sport/dynamic mode?
Have you done any longer highway drives to see what kind of mpg it displays?

Might not hurt to pull your MAP sensors and clean them (or replace them, not expensive). Otherwise, plugs, fuel pump/filter, and carbon cleaning.

[MarcMiller]

Are you always in sport/dynamic mode?
Have you done any longer highway drives to see what kind of mpg it displays?

Might not hurt to pull your MAP sensors and clean them (or replace them, not expensive). Otherwise, plugs, fuel pump/filter, and carbon cleaning.

Lately I’ve strictly been driving in Drive mode. I use individual but D for everyday driving. I haven’t done any long distance highway drives much but next time I’ll check the mpg. Thanks for the help.

Definitely gonna look into carbon clean ASAP too.


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[S3NICK]

I think he means the drive mode selector. Are you driving in Auto, Comfort, Dynamic, or Individual. Shouldn't make THAT big of a difference though.

[MarcMiller]

I think he means the drive mode selector. Are you driving in Auto, Comfort, Dynamic, or Individual. Shouldn't make THAT big of a difference though.

I drive in Individual but have it mainly set to comfort minus engine and exhaust set to dynamic.


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[n8vs3]

Lately I’ve strictly been driving in Drive mode. I use individual but D for everyday driving. I haven’t done any long distance highway drives much but next time I’ll check the mpg. Thanks for the help.

Definitely gonna look into carbon clean ASAP too.


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https://youtu.be/OM0M2bQM-ag

Just came across this video on EA888 gen3 decarbonization

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[MarcMiller]

https://youtu.be/OM0M2bQM-ag

Just came across this video on EA888 gen3 decarbonization

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Thank you sir. Someone else sent me a video similar to this. I might do it with a tech on a Saturday sometime soon.


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[jinetix]

I normally get around 200-220 miles to the tank but I mostly drive short distances in the city.

Here's a pic showing 16.2mpg over the span of 2313 miles and an average of 13mph.


Here's a pic showing 26.1mpg on the highway averaging 33mph over 56 minutes of driving.


A carbon cleaning of the intake valves should help a bit especially given the mileage. I'm getting the same mileage as you though with a low mileage car.. wouldn't worry too much.

[XMetal]

I have a 2015 S3 with 76k miles. I do a mix of city and highway driving and I hit 300+ miles every tank, roughly 26-27 mpg. Stock. I’m hardly ever in sport/dynamic but I’m always crushing on the highway >80mph.

Did a carbon cleaning, it was a mess in there. Intake manifold has to come off to do this. I also did spark plugs and swapped both MAP sensors.

You're driving the car all wrong

Mileage is highly dependent on your right foot. When my wife drives it, she can average 28-30 mpg easily. She drives it in Auto/Normal. It only average between 16-17 mpg for me in Manual mode (Normal shifts too early and Dynamic hangs onto the gears too long). Although, I love Dynamic's behavior in canyon runs.

OP - try to lighten your right foot a bit. Have you tried comfort/efficient mode (forgot which one we get)? You should be able to hit the high 20's or low 30's if you cruise below 65mph. I have been able to see 32-33 mpg on long stretches doing 80mph on road trips.

[MarcMiller]

You're driving the car all wrong

Mileage is highly dependent on your right foot. When my wife drives it, she can average 28-30 mpg easily. She drives it in Auto/Normal. It only average between 16-17 mpg for me in Manual mode (Normal shifts too early and Dynamic hangs onto the gears too long). Although, I love Dynamic's behavior in canyon runs.

OP - try to lighten your right foot a bit. Have you tried comfort/efficient mode (forgot which one we get)? You should be able to hit the high 20's or low 30's if you cruise below 65mph. I have been able to see 32-33 mpg on long stretches doing 80mph on road trips.

Everything I’ve mentioned has ONLY been in comfort.


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[Brandon.august]

You're driving the car all wrong

Mileage is highly dependent on your right foot. When my wife drives it, she can average 28-30 mpg easily. She drives it in Auto/Normal. It only average between 16-17 mpg for me in Manual mode (Normal shifts too early and Dynamic hangs onto the gears too long). Although, I love Dynamic's behavior in canyon runs.

OP - try to lighten your right foot a bit. Have you tried comfort/efficient mode (forgot which one we get)? You should be able to hit the high 20's or low 30's if you cruise below 65mph. I have been able to see 32-33 mpg on long stretches doing 80mph on road trips.

I can see 32-33 mpg at 80mph in a 2018 with that 7-speed, but not at 3500 rpms in a 2017 or older haha. And yeah, I’ve been babying it through these fuel/stalling issues I’m having. Soon, soon. I’m actually thinking about getting a 2018... I want the 7-speed.

[MarcMiller]

So I can drive in dynamic without my mpg being really affected? It’s so much funnier driving in dynamic but I’ve been trying to baby it.


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[MarcMiller]

Also, here’s an update from this morning..


Current full tank I’m at 170 miles with roughly a half tank left. I’ve been really focusing on not driving in boost, not in Sport, and very light on the pedal. Even at 170 miles with a half tank I wouldn’t be surprised if I only get 220 miles out of it. Sure it’s better than what I’ve been getting but you’d think since I’m focusing on my MPG on this tank so much that it should definitely be more.

[XMetal]

I can see 32-33 mpg at 80mph in a 2018 with that 7-speed, but not at 3500 rpms in a 2017 or older haha. And yeah, I’ve been babying it through these fuel/stalling issues I’m having. Soon, soon. I’m actually thinking about getting a 2018... I want the 7-speed.

Good point - forgot about the 7spd vs 6spd.

[MarcMiller]

Another update..

Just filled it up. I prob would’ve gotten around 250 miles to the tank but wanted to refill before it was too low. I used to drive my A3 until it said 0 miles almost every time. Maybe it’s not as bad as I thought.

[Brandon.august]

Another update..

Just filled it up. I prob would’ve gotten around 250 miles to the tank but wanted to refill before it was too low. I used to drive my A3 until it said 0 miles almost every time. Maybe it’s not as bad as I thought.

How many gallons did it take?

[MarcMiller]

How many gallons did it take?

Almost 12 exactly


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[Brandon.august]

Almost 12 exactly


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Around 19mpg, that’s not bad.

[MarcMiller]

Around 19mpg, that’s not bad.

That’s me driving very soft the whole tank. I guess I should get used to it lol


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[Brandon.august]

That’s me driving very soft the whole tank. I guess I should get used to it lol


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Sounds like it does need maintenance though. I get 27 driving soft, I cruise at 80+ on the highway, and plenty of spirited driving here and there. I typically avoid fast starts from a dead stop but play on the highway.

[MarcMiller]

Sounds like it does need maintenance though. I get 27 driving soft, I cruise at 80+ on the highway, and plenty of spirited driving here and there. I typically avoid fast starts from a dead stop but play on the highway.

Think I should start with a carbon cleaning?


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[n8vs3]

Regarding MPG...if your gas is oxygenated (i.e. 10% ethanol blend) like in many Western States. Expect MPG that is slightly less than advertised.

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[MarcMiller]

Regarding MPG...if your gas is oxygenated (i.e. 10% ethanol blend) like in many Western States. Expect MPG that is slightly less than advertised.

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I’m not really sure about that I’m just comparing to my 2016 A3 lol

[Brandon.august]

Think I should start with a carbon cleaning?


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Carbon cleaning, spark plugs, clean up or replace the MAP sensors (electrical cleaner or soak them in isopropanol), air filter. Might be worth cleaning the injectors while you're in there for a carbon cleaning (not expensive to have done but you'll have to be ok with the car being down for a couple days unless you find a local shop with quick turnaround).

Also, consider tire pressure and rim size, especially when comparing to your A3.